The government announced on Tuesday that all mobile telecom companies will have to bring in voice or text alerts for incoming overseas calls, which mimic Hong Kong numbers, from the beginning of next month.

The Office of the Communications Authority (OFCA) said the move is intended to better protect users from potential scam calls.

The Director-General of Communications, Chaucer Leung, said while four major mobile operators have already adopted the system, it will be expanded to all telecom companies from May.

Users will receive a standard alert message: ‘Call is from outside Hong Kong. Beware of deception’ when they receive calls with caller numbers prefixed with '+852' – indicating that they originate outside Hong Kong but are disguised as local numbers.

The service will be provided free of charge, and users won't need to install any mobile apps or change their phone settings to use it.

Leung added that OFCA hopes to roll out a system by the end of the year to combat scams that use SMS messages.

"For our SMS registration scheme, we require all the legitimate companies to register their sender address. For example, if this is an ABC company, it can register as ABC. Then all other entities cannot use ABC to send SMS to other people," he said.

"OFCA is working with police, telecom operators, banks, Hong Kong Monetary Authority to establish a registration scheme for SMS sender addresses... we are working out the technical arrangements and implementation details for pilot run before the end of this year.”